1. Field of Invention
The present invention relates to a surface texture measuring instrument for measuring a surface roughness, waviness and profile of a workpiece by moving a detector having a stylus and a skid at a distal end thereof along a measurement surface.
2. Description of Related Art
A surface texture measuring instrument has a detector having a stylus at a distal end thereof and a drive unit for moving the detector along a measurement surface, where the stylus is in contact with the measurement surface to detect displacement of the stylus as a measurement data.
The stylus is attached to a detector body in a seesawing manner, and a skid is attached to the detector body to cover a distal end of the stylus. The skid is attached to the detector body by a bolt so that the skid is detachable from the detector body.
During measurement with skid (referred to xe2x80x9cskid measurementxe2x80x9d hereinafter), the skid is fixed to the detector body for conducting measurement. Such skid measurement is used in order to remove the waviness component and to detect only the roughness component data when the measurement surface has both the waviness and the roughness. During the measurement, the detector is moved while both the stylus and the skid are in contact with the measurement surface.
During the skid measurement, the skid has to be constantly in contact with the measurement surface. Accordingly, the detector and the drive unit are conventionally connected by a leaf spring, so that the skid is pressed toward the measurement surface by the leaf spring (Japanese Patent Application Laid-Open Publication No. Hei 11-190621).
Skidless measurement with the skid detached from the detector body is used for measuring cross section and straightness of the workpiece by detecting all of concavo-convex data of the measurement surface including waviness etc. During the skidless measurement, the detector is moved while only the stylus is in contact with the measurement surface.
In the conventional arrangement, the skid measurement is conducted by fixing a skid to the detector body by a bolt and the skidless measurement is conducted by detaching the skid from the detector body.
In a surface texture measuring instrument, the skid has to be exchanged into a skid of different type.
In this case, it is desirable to change the pressing force of the skid toward the measurement surface. However, since the leaf spring for pressing the skid at the distal end of the detector presses the measurement surface and has a constant spring force, such demand has not been sufficiently met.
An object of the present invention is to provide a surface texture measuring instrument capable of easily switching the skid measurement and the skidless measurement and capable of controlling a pressing force of the skid toward the measurement surface.
For attaining the above object, in the present invention, a force for biasing the detector is controlled and movement of the detector in a pre-load force direction is restricted for conducting the skidless measurement.
More specifically, a surface texture measuring instrument according to the present invention is characterized in having a detector with a stylus for measuring the surface texture and a detachable skid at a distal end thereof; a drive unit for moving the detector along a measurement surface; a pre-load means for biasing the detector to press the skid onto the measurement surface; a pre-load force controller for controlling a pre-load force of the pre-load means; and a restriction means for restricting a movement of the detector in a direction of the pre-load force when the pre-load force controller applies a predetermined pre-load force to the detector, thus conducting the skidless measurement.
In the present invention, in order to conduct the skidless measurement, a predetermined pre-load force is applied to the detector by the pre-load force controller.
Then, the skid does not move on account of a great pre-load force caused to the detector even when a force opposite to the biasing direction is applied. Further, since the movement of the detector in the biasing direction is restricted by the restriction means, the skid does not move in the biasing direction, thus being xe2x80x9clockedxe2x80x9d.
In the above condition, the detector is moved by the drive unit while the stylus is in contact with the measurement surface, so that all the concavo-convex data on the measurement surface is detected.
On the other hand, for conducting the skid measurement, a pre-load force less than the predetermined value is applied to the detector by the pre-load force controller.
Then, though the skid is biased by the pre-load force caused to the detector, the movement in the biasing direction is not restricted by the restriction means.
In the above condition, when the detector is moved by the drive unit while the skid and the stylus are in contact with the measurement surface, the skid is displaced along the waviness on the measurement surface, and the displacement of the stylus relative to the skid is detected as a data, such as surface roughness.
Then, the pre-load force controller is operated to adjust the pre-load force applied to the detector when the skid is exchanged into a different type skid.
Accordingly, the pre-load force applied to the detector can be controlled by the pre-load force controller, thus easily controlling the pressing force against the measurement surface of the skid.
Furthermore, since the skidless measurement can be conducted while restricting the movement of the detector toward the biasing direction when the predetermined pre-load force is applied to the detector, the skid measurement and the skidless measurement can be easily switched by operating the pre-load force controller.
In the present invention, the pre-load means may preferably include a holding pre-load means for holding the detector and a pressing pre-load means for pressing the detector against the measurement surface.
According to the above arrangement, since the minimum required pre-load force is obtained by the holding pre-load means and the adjusting pre-load force can be controllably applied by the pressing pre-load means, the pre-load force of the detector can be easily adjusted.
In the present invention, the holding pre-load means and the pressing pre-load means may preferably be first and second leaf springs with the first ends secured to either one of the detector or the drive unit at a predetermined gap and the second ends attached to the other one of the detector or the drive unit. The pre-load force controller is an adjustment screw for moving the second end of the second leaf spring toward and away from the first leaf spring to adjust the pre-load force of the detector against the measurement surface, and the restriction means is a stopper for restricting the movement of the detector in a biasing direction of the detector when the pre-load force of the detector is increased by screwing in the adjustment screw.
According to the above arrangement, since the second end of the second leaf spring comes adjacent to the second end of the first leaf spring by screwing in the adjustment screw, a pre-load force (spring force) for moving the first end of the second leaf spring away from the first end of the first leaf spring is applied, thus applying a great pre-load force onto the detector. Then, a great pressing force is applied to the skid in contact with the measurement surface, on account of the pre-load force applied to the detector.
When the adjustment screw is screwed at the maximum, the pre-load force of the detector relative to the drive unit is enlarged and the movement of the detector toward the biasing direction is restricted by the stopper, thus locking the detector.
Accordingly, in the above arrangement, the two pre-load means for holding and pressing are composed of the leaf springs, thus the structure of the pre-load means can be simplified.
Further, since the pre-load force controller is composed of the screw member, the pre-load force can be easily controlled by adjusting a screwing amount of the screw.
In the present invention, the surface texture measuring instrument may preferably have an auxiliary pre-load means for biasing the skid toward the measurement surface.
According to the above arrangement, the pre-load force of the detector can be minutely adjusted by the auxiliary pre-load means in addition to the pre-load means.
Further, by constructing the auxiliary pre-load means with a helical spring provided between the detector and the drive unit, the structure of the device can be simplified.